Whole-cell patch clamp electrophysiology of neurons is a “gold standard” technique for high-fidelity analysis of the biophysical mechanisms of neural computation and pathology. Whole-cell patch clamp electrophysiology of neurons in vivo enables the recording of electrical events in cells with great precision and supports a wide diversity of morphological and molecular analysis experiments important for the understanding of single-cell and network functions in the intact brain. However, high levels of skill are required in order to perform in vivo patching, and the process is time-consuming and painstaking.
In whole-cell patch clamp electrophysiology, a glass pipette electrode is used to gain electrical and molecular access to the inside of a cell. It permits high-fidelity recording of electrical activity in neurons embedded within intact tissue, such as in brain slices, or in vivo. Whole-cell patch clamp recordings [Hamill, O. P., Marty, A., Neher, E., Sakmann, B. & Sigworth, F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch 391, 85-100 (1981); Margrie, T. W., Brecht, M. & Sakmann, B. In vivo, low-resistance, whole-cell recordings from neurons in the anaesthetized and awake mammalian brain. Pflugers Arch 444, 491-498 (2002)] of the electrical activity of neurons in vivo, which utilize the glass micropipettes to establish electrical and molecular access to the insides of neurons embedded in intact tissue, exhibit signal quality and temporal fidelity sufficient to report synaptic and ion-channel mediated subthreshold events of importance for understanding how neurons compute, and how their physiology can be modulated by brain disorders or pharmaceuticals. In vivo patching of cells in intact brain presents several capabilities that make it of great use: the recordings present extremely high signal-to-noise ratios and thus can be used to reveal subthreshold responses such as synaptic or ion channel events. Current can be delivered into a pipette to drive or silence the cell being recorded, or to support the characterization of specific receptors or channels in the cell.
Whole-cell patch clamping of cells in intact tissue also allows for infusion of chemicals and the extraction of cell contents. Molecular access to the cell enables infusion of dyes for morphological visualization, as well as extraction of cell contents for transcriptomic single-cell analysis [Eberwine, J. et al. Analysis of gene expression in single live neurons. Proc Natl Acad Sci USA 89, 3010-3014 (1992)], thus enabling integrative analysis of molecular, anatomical, and electrophysiological information about single neurons in intact tissue.
However, whole-cell patch clamping of cells in intact tissue is laborious, being something of an art to perform, especially in vivo. Although protocols exist for performing whole-cell patch clamp recording in such conditions, much practice is required by individual investigators to master the technique, since each step in the process of looking for a neuron and establishing the recording requires intuition as well as fast judgment and action. This has limited adoption in neuroscience to a small number of labs, and also precludes systematic or scalable in vivo patch clamping experiments.